lsp-buf: change buf CLI args

[suzuki]

WHAT

Change args of buf

WHY

• The lsp command in buf has graduated from beta
  • https://github.com/bufbuild/buf/releases/tag/v1.59.0

    Promote buf beta lsp to buf lsp serve. Command buf beta lsp is now deprecated.

• No longer times out by default
  • https://github.com/bufbuild/buf/releases/tag/v1.60.0

    Update default value of --timeout flag to 0, which results in no timeout by default.

• Use logformat default (text)
  • fix(lsp-bufls): Resolve timeout issues #4739 (comment)

[Copilot]

Pull request overview

This PR updates the buf CLI arguments to use the stable LSP command and remove redundant flags following recent buf releases.

Key Changes:

• Migrated from deprecated buf beta lsp to stable buf lsp serve command (graduated in buf v1.59.0)
• Removed --timeout 0 flag (now the default as of buf v1.60.0)
• Removed --log-format json flag (using text format default)

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[jcs090218]

Thank you!